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Message-ID: <CABi2SkU2yX_Pbr6=6uEiQnro88O5Mhq3NLwOsy=A=Qa5xeC6Yw@mail.gmail.com>
Date: Thu, 17 Oct 2024 09:20:20 -0700
From: Jeff Xu <jeffxu@...omium.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: akpm@...ux-foundation.org, keescook@...omium.org,
torvalds@...ux-foundation.org, usama.anjum@...labora.com, corbet@....net,
Liam.Howlett@...cle.com, jeffxu@...gle.com, jorgelo@...omium.org,
groeck@...omium.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-mm@...ck.org, jannh@...gle.com,
sroettger@...gle.com, pedro.falcato@...il.com,
linux-hardening@...r.kernel.org, willy@...radead.org,
gregkh@...uxfoundation.org, deraadt@...nbsd.org, surenb@...gle.com,
merimus@...gle.com, rdunlap@...radead.org
Subject: Re: [PATCH] munmap sealed memory cause memory to split (bug)
On Thu, Oct 17, 2024 at 1:18 AM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> NACK. Greg's bot got to it but...
>
> As per Greg's bot, no signed-off-by line.
>
Sorry for confusion, I wasn't meant to send this as a PATCH, but
reporting the issue.
The diff was just sent as reference to repro the bug, and I forgot to
remove PATCH from the title. I apologize for the confusion.
-Jeff
> The subject should be something about adding a test.
>
> You later say you are somehow dependning on things (what?) to make this work but
> it's broken.
>
> Jeff - you're doing things that were raised on previous reviews as if we
> never said them. It's starting to get annoying now. Please try to listen to
> upstream.
>
> On Thu, Oct 17, 2024 at 02:26:27AM +0000, jeffxu@...omium.org wrote:
> > From: Jeff Xu <jeffxu@...gle.com>
> >
> > It appears there is a regression on the latest mm,
> > when munmap sealed memory, it can cause unexpected VMA split.
> > E.g. repro use this test.
>
> This is an unacceptably short commit message. You've been told about this
> before.
>
> > ---
> > tools/testing/selftests/mm/mseal_test.c | 76 +++++++++++++++++++++++++
> > 1 file changed, 76 insertions(+)
> >
> > diff --git a/tools/testing/selftests/mm/mseal_test.c b/tools/testing/selftests/mm/mseal_test.c
> > index fa74dbe4a684..0af33e13b606 100644
> > --- a/tools/testing/selftests/mm/mseal_test.c
> > +++ b/tools/testing/selftests/mm/mseal_test.c
> > @@ -1969,6 +1969,79 @@ static void test_madvise_filebacked_was_writable(bool seal)
> > REPORT_TEST_PASS();
> > }
> >
> > +static void test_munmap_free_multiple_ranges_with_split(bool seal)
> > +{
> > + void *ptr;
> > + unsigned long page_size = getpagesize();
> > + unsigned long size = 12 * page_size;
> > + int ret;
> > + int prot;
> > +
> > + setup_single_address(size, &ptr);
> > + FAIL_TEST_IF_FALSE(ptr != (void *)-1);
>
> I'm not going to accept any test where you do:
>
> FAIL_TEST_IF_FALSE(<negation>)
>
> As that's totally unreadable. I asked you before for justification and you
> didn't provide it, no other tests appear to do this, I wrote thousands of
> lines of tests recently without doing this - stop it.
>
> Also referene MAP_FAILED here please. You've been told before.
>
> > +
> > + /* seal the middle 4 page */
> > + if (seal) {
> > + ret = sys_mseal(ptr + 4 * page_size, 4 * page_size);
> > + FAIL_TEST_IF_FALSE(!ret);
> > +
> > + size = get_vma_size(ptr, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
>
> Again, you've been told before, stop referencing numbers instead of
> PROT_... flags.
>
> OK I'm stopping at this point, you _must listen to review_ Jeff.
>
> > +
> > + size = get_vma_size(ptr + 4 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > +
> > + size = get_vma_size(ptr + 8 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > + }
> > +
> > + /* munmap 4 pages from the third page */
> > + ret = sys_munmap(ptr + 2 * page_size, 4 * page_size);
> > + if (seal) {
> > + FAIL_TEST_IF_FALSE(ret);
> > + FAIL_TEST_IF_FALSE(errno == EPERM);
> > +
> > + size = get_vma_size(ptr, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > +
> > + size = get_vma_size(ptr + 4 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > +
> > + size = get_vma_size(ptr + 8 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > + } else
> > + FAIL_TEST_IF_FALSE(!ret);
> > +
> > + /* munmap 4 pages from the sealed page */
> > + ret = sys_munmap(ptr + 6 * page_size, 4 * page_size);
> > + if (seal) {
> > + FAIL_TEST_IF_FALSE(ret);
> > + FAIL_TEST_IF_FALSE(errno == EPERM);
> > +
> > + size = get_vma_size(ptr + 4 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > +
> > + size = get_vma_size(ptr + 4 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > +
> > + size = get_vma_size(ptr + 8 * page_size, &prot);
> > + FAIL_TEST_IF_FALSE(size == 4 * page_size);
> > + FAIL_TEST_IF_FALSE(prot == 4);
> > + } else
> > + FAIL_TEST_IF_FALSE(!ret);
> > +
> > + REPORT_TEST_PASS();
> > +}
> > +
> > +
> > int main(int argc, char **argv)
> > {
> > bool test_seal = seal_support();
> > @@ -2099,5 +2172,8 @@ int main(int argc, char **argv)
> > test_madvise_filebacked_was_writable(false);
> > test_madvise_filebacked_was_writable(true);
> >
> > + test_munmap_free_multiple_ranges_with_split(false);
> > + test_munmap_free_multiple_ranges_with_split(true);
> > +
> > ksft_finished();
> > }
> > --
> > 2.47.0.rc1.288.g06298d1525-goog
> >
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